Cold air to descend next week

It's looking increasingly likely as if a buckle in the jet stream will allow the first real shot of cold air this season to push into parts of the continental United States next week.

While somewhat-cooler conditions could reach the Carolinas, it looks for now as if the really chilly stuff will be confined to areas northwest of the Charlotte region.

But the configuration of the cold air outbreak could provide a hint of what is to come this winter, if you believe some of the long-range forecasts.

It has been a mild month so far for the Midwest and much of the East. Temperatures this month in places like Chicago and St. Louis have averaged 6 to 7 degrees above average. In the Charlotte area, temperatures have been only a few degrees above average.

All that appears likely to change. Low pressure in Hudson Bay and high pressure south of Greenland could provide a blocking pattern like the kind that bring bitterly cold air and snowstorms to the central and eastern United States in the winter. In late October, of course, there won't be the bitter cold and widespread snow, although parts of the Midwest could see flurries.

The best guess now is that the cold air will funnel southward, creating the typical "U-shaped" pattern that we see in blocking situations. Areas above the outline of the letter U will be in the cold air. That jet stream dip will come southward from Canada into the Dakota, then down across the Midwest, bottoming out in Tennessee and then curving northeast across Virginia and the Mid Atlantic.

If that happens, say goodbye to the growing season in much of the Tennessee and Ohio valleys, along with the Great Lakes.

Nearly all of the Carolinas would stay on the milder side of the cold air outbreak in that scenario.

I've seen a couple long-range winter forecasts that predict the same general pattern from November through February.  We'll talk more about that in coming days.